Date:         Wed, 9 Jan 2002 12:21:58 -0800
Reply-To:     Steve Sullivan <steveis@SPEAKEASY.ORG>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Steve Sullivan <steveis@SPEAKEASY.ORG>
Subject:      Re: A Snow Story (Whoa-vanagon!!!) and Lessons Learned
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Something else I thought of you all might find interesting. I once read that
tests had been done that determined a slight about of wheel slippage
actually can provide increased traction (or forward movement at least).

 The biggest mistake most people make when they are "stuck" is spinning heck
out of their tires trying to, I don't know, burn their way down through the
ice? Who knows. As any experienced snow driver knows, giving as little power
(torque, actually) to the drive wheels as possible, but enough not to stall
the engine or spin the wheels, is the key to getting moving again. So,
someone with the low gear on a syncro, for example, could just let the
clutch out without giving it any gas and possibly drive off, because the
gear is low enough to let the engine move the vehicle without needing much
power. At speed, say trying to get up a hill at 30 MPH, putting it in as
high a gear as possible (to lower the amount of torque the engine can
produce) while not stalling or dramatically lugging the engine can help.

Next time, try this: allow the drive wheel/s to spin just a wee bit
(experiment) and you'll be surprised. I was heading up a highway hill at
about 55 MPH, trying to maintain enough momentum to crest the hill. Then it
started happening, the wheels started spinning, so I powered down to regain
traction, which slows us down, and on and on and soon I'm getting down to 20
MPH and I'll lose it in seconds and have to stop and chain up. I start
stabbing the accelerator, letting the wheels spin until we start sliding
sideways, then ease off, start spinning again, and so on, and it seemed to
be just enough to get us up and over the hill more than once.

I learned this in an article about railroad locomotives. See, a locomotive
has a diesel engine connected to a giant generator that provides power to
electric "traction" motors on each axle that are actually what moves the
train. Engineer winds up the diesel, builds up electricity, the train moves,
he powers down, it's an interesting delayed reaction process. But off topic.

They used to have a light on the dash that lit if any of the axles slipped
at all. The engineer simply reduced engine power to compensate. But they
discovered that up if the electric motors slipped up to 35%, it increased
traction (forward motion) considerably. So now it's the electricity flow to
the motors is controlled by computer to allow for wheel slippage when
needed. I don't remember that actual facts or numbers (maybe I pulled 35%
out of my exhaust pipe), but I know that's the basic gist. Love to hear from
someone who knows actual data or how this works.

Steve
Calvin, the 84 Westy
Hobbes, the imaginary Syncro Westy